Introduction to Toxicology

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Questions and Answers

What is the mechanism of Type III hypersensitivity?

Mediated by a T-cell response

Involves the binding of antigens to IgE antibodies

Initiated by direct effects on mast cells

Formation of immune complexes that cause local inflammation (correct)

Which of the following is an example of Type IV hypersensitivity?

Hemolytic anemia

Serum sickness

Contact dermatitis from poison ivy (correct)

Anaphylaxis

How long after exposure do symptoms of Type IV hypersensitivity typically appear?

48-72 hours (correct)

12-24 hours

Immediately

24-48 hours

What is NOT a characteristic of Type III hypersensitivity?

Mediated by T cells Signup and view all the answers

What triggers 'red man syndrome' during drug exposure?

Direct effect of drug on mast cells Signup and view all the answers

What is defined as any substance that can harm a living organism?

Poison Signup and view all the answers

Which of the following statements reflects the idea of threshold dose in toxicology?

Every drug has a specific dose below which it is harmless. Signup and view all the answers

What kind of toxic reaction is classified as a Type A reaction?

Expected from pharmacological actions Signup and view all the answers

Which drug is known to cause liver damage as a result of overdose?

Acetaminophen Signup and view all the answers

What is one of the main concerns regarding genotoxicity in cancer chemotherapy?

It can cause DNA damage in both cancer and normal cells. Signup and view all the answers

Which of the following is NOT a mechanism by which drugs can induce toxicity?

Homeostasis Signup and view all the answers

What is the estimated annual cost associated with adverse drug effects due to dosing errors?

$1.5 billion to $5.5 billion Signup and view all the answers

Which of the following is NOT an example of pharmacological toxicity?

Liver damage from acetaminophen overdose Signup and view all the answers

What mechanism is primarily involved in Type I hypersensitivity responses?

Degranulation of mast cells mediated by IgE Signup and view all the answers

What is a consequence of 'on target' adverse effects?

Inappropriate concentrations of the drug Signup and view all the answers

Which type of hypersensitivity is associated with mast cell degranulation?

Type I Signup and view all the answers

What type of reaction can caused by antibodies mediating the lysis of cells, typically red blood cells?

Type II hypersensitivity Signup and view all the answers

What is a significant complication associated with off-target drug binding to the hERG potassium channel?

Cardiac arrhythmias Signup and view all the answers

Which drug class can develop 'off-target' adverse effects due to binding to B1 and B2 receptors?

Beta-agonists Signup and view all the answers

A notable example of Type II hypersensitivity can include which of the following conditions?

Heparin-induced thrombocytopenia Signup and view all the answers

What is the primary immune mechanism responsible for Type I hypersensitivity reactions?

IgE-mediated mast cell degranulation Signup and view all the answers

Study Notes

Toxicology

Toxicology studies the unwanted harmful effects of drugs and chemicals.
A poison is any substance that can harm a living organism.
Almost all drugs have a threshold dose beyond which they become poisonous.
Even excess carbohydrates can be harmful.
Paracelsus stated, "All things are poison, and nothing is without poison. Solely the dose determines that a thing is not a poison".
About 2 million hospitalized patients experience adverse drug reactions annually in the U.S.
About 100,000 of these are fatal.
Dosing errors affect an estimated 775,000 people annually, costing $1.5 to $5.5 billion.

Types of Effects

Effects can be desirable or undesirable.
Undesirable effects can be non-deleterious (side effects) or deleterious (toxic effects).

Pharmacological Toxicity

Pharmacological toxicity is an extension of a drug's therapeutic effect due to increased dose or duration of treatment.
Type A reactions are expected from a drug's pharmacological actions.
- Examples include central nervous system depression from high doses of barbiturates and a severe drop in blood pressure from high doses of sodium nitroprusside. Also, extrapyramidal motor disorders can occur from prolonged use of certain antipsychotics.

Pathological Toxicity

Pathological toxicity manifests as pathological effects in the body.
- Example: Liver damage from acetaminophen overdose.
- Another example is the antifungal drug amphotericin B and the antibiotic gentamicin, which can cause kidney damage.
Genotoxicity damages DNA, caused by drugs, chemicals, ionizing radiation damaging DNA.
- Examples include nitrogen mustards, nitrosoureas, alkyl sulfonates, and cisplatin.

Mechanisms of Drug Toxicity

On-target effects result from drug binding to intended receptors, but at inappropriate concentrations or kinetics or in wrong tissues.
- Example: Sedative effects from antihistamines binding to wrong receptors.
Off-target effects occur when drugs bind to unintended receptors.
- Example: Disruption of potassium channels leading to cardiac arrhythmias.
- Off-target binding can also happen when receptors, normally for specific organ/tissue, are inappropriately targeted.

Hypersensitivity Reactions (Type B)

Hypersensitivity reactions (Type B) are mediated by the immune system.
- Four types exist:
  - Type I (Immediate): IgE-mediated, rapid onset. (e.g. penicillin)
  - Type II (Cytolytic): Antibody-mediated destruction of cells (e.g., some blood disorders)
  - Type III (Immune Complex): Immune complex deposition in tissues (e.g., serum sickness)
  - Type IV (Delayed): T-cell-mediated, delayed onset (e.g., contact dermatitis)

Poisoning Cases

Common substances associated with poisonings.
Reasons for these cases are medication errors, drug interactions etc.

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Description

This quiz covers the fundamental concepts of toxicology, including the definition of poisons, the impact of drug dosing, and the types of effects drugs can have. Explore the delicate balance between therapeutic effects and toxic reactions. Gain insights into the statistics surrounding adverse drug reactions and their significance in healthcare.